How long should I stay out of Thailand to get a new 30-day entry upon return?

I have flown to KL and back, same day.

Providing you can show sufficient funds and a flight out of the country when your entry visa expires you will never get interrogated or questioned

You might get a suggestion that there are alternative visas available to help you but you will “Never” be questioned further

All the bullshit going around about being pulled aside and refused entry is total garbage

Remember Thailand want your $$$$

If over 50 get an agent to do a Non O visa for you with multiple entry then you can come and go as you please 🙏

There's never been a limited number of times, so your information is wrong on that one. However forget about 7-8 months without a visa. Your best bet is to get a METV from UK before you leave. This will give you up to nine months with just two border bounces

Nothing has changed so I'm not sure what you mean "unlike before"

There's no limit to how many times you can enter without a visa if you're flying to Thailand. But eventually you're going to be stopped at passport control and they're going to ask why you're spending so much time in Thailand without a long term visa. Eventually they'll say you're abusing the system and you're not a tourist and they'll deny entry.

It could happen the 2nd time, 3rd time, 4th time, never. It's all at the discretion of the immigration officer you're standing in front of.